lowzag 2.3.0 Coefficient storage is the low-frequency corner and nothing else, row-major, instead of the shortest zigzag prefix containing it. Summed peak_alloc over the corpus falls 21.7% at 1/2 and 21.8% at 1/4; the 12 MP 4:2:0 reference file goes 23.0 -> 19.6 MB at 1/2 and 8.9 -> 6.8 MB at 1/4. Decoded output is unchanged, bit for bit, on every valid file at every scale, and lowzag_estimate().alloc_bytes still equals the decode's peak_alloc exactly. Decode is 3.3% to 5.0% faster. The AC refinement scan's nonzero test now reads the nonzero bitmap wherever there is one, which is T.81 G.1.2.3's predicate; the stored value is used only where every coefficient is stored. See the CHANGELOG.